/*
 * Copyright 1999-2018 Alibaba Group Holding Ltd.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.alibaba.csp.sentinel.dashboard.repository.metric;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import java.util.concurrent.ConcurrentHashMap;
import java.util.stream.Collectors;

import com.alibaba.csp.sentinel.dashboard.datasource.entity.MetricEntity;
import com.alibaba.csp.sentinel.util.StringUtil;

import com.googlecode.concurrentlinkedhashmap.ConcurrentLinkedHashMap;
import org.springframework.stereotype.Component;

/**
 * Caches metrics data in a period of time in memory.
 *
 * @author Carpenter Lee
 * @author Eric Zhao
 */
@Component
public class InMemoryMetricsRepository implements MetricsRepository<MetricEntity> {

	private static final long MAX_METRIC_LIVE_TIME_MS = 1000 * 60 * 5;

	/**
	 * {@code app -> resource -> timestamp -> metric}
	 */
	private Map<String, Map<String, ConcurrentLinkedHashMap<Long, MetricEntity>>> allMetrics = new ConcurrentHashMap<>();

	@Override
	public synchronized void save(MetricEntity entity) {
		if (entity == null || StringUtil.isBlank(entity.getApp())) {
			return;
		}
		allMetrics.computeIfAbsent(entity.getApp(), e -> new ConcurrentHashMap<>(16))
				.computeIfAbsent(entity.getResource(),
						e -> new ConcurrentLinkedHashMap.Builder<Long, MetricEntity>()
								.maximumWeightedCapacity(MAX_METRIC_LIVE_TIME_MS).weigher((key, value) -> {
									// Metric older than {@link #MAX_METRIC_LIVE_TIME_MS}
									// will be removed.
									int weight = (int) (System.currentTimeMillis() - key);
									// weight must be a number greater than or equal to
									// one
									return Math.max(weight, 1);
								}).build())
				.put(entity.getTimestamp().getTime(), entity);
	}

	@Override
	public synchronized void saveAll(Iterable<MetricEntity> metrics) {
		if (metrics == null) {
			return;
		}
		metrics.forEach(this::save);
	}

	@Override
	public synchronized List<MetricEntity> queryByAppAndResourceBetween(String app, String resource, long startTime,
			long endTime) {
		List<MetricEntity> results = new ArrayList<>();
		if (StringUtil.isBlank(app)) {
			return results;
		}
		Map<String, ConcurrentLinkedHashMap<Long, MetricEntity>> resourceMap = allMetrics.get(app);
		if (resourceMap == null) {
			return results;
		}
		ConcurrentLinkedHashMap<Long, MetricEntity> metricsMap = resourceMap.get(resource);
		if (metricsMap == null) {
			return results;
		}
		for (Entry<Long, MetricEntity> entry : metricsMap.entrySet()) {
			if (entry.getKey() >= startTime && entry.getKey() <= endTime) {
				results.add(entry.getValue());
			}
		}
		return results;
	}

	@Override
	public List<String> listResourcesOfApp(String app) {
		List<String> results = new ArrayList<>();
		if (StringUtil.isBlank(app)) {
			return results;
		}
		// resource -> timestamp -> metric
		Map<String, ConcurrentLinkedHashMap<Long, MetricEntity>> resourceMap = allMetrics.get(app);
		if (resourceMap == null) {
			return results;
		}
		final long minTimeMs = System.currentTimeMillis() - 1000 * 60;
		Map<String, MetricEntity> resourceCount = new ConcurrentHashMap<>(32);

		for (Entry<String, ConcurrentLinkedHashMap<Long, MetricEntity>> resourceMetrics : resourceMap.entrySet()) {
			for (Entry<Long, MetricEntity> metrics : resourceMetrics.getValue().entrySet()) {
				if (metrics.getKey() < minTimeMs) {
					continue;
				}
				MetricEntity newEntity = metrics.getValue();
				if (resourceCount.containsKey(resourceMetrics.getKey())) {
					MetricEntity oldEntity = resourceCount.get(resourceMetrics.getKey());
					oldEntity.addPassQps(newEntity.getPassQps());
					oldEntity.addRtAndSuccessQps(newEntity.getRt(), newEntity.getSuccessQps());
					oldEntity.addBlockQps(newEntity.getBlockQps());
					oldEntity.addExceptionQps(newEntity.getExceptionQps());
					oldEntity.addCount(1);
				}
				else {
					resourceCount.put(resourceMetrics.getKey(), MetricEntity.copyOf(newEntity));
				}
			}
		}
		// Order by last minute b_qps DESC.
		return resourceCount.entrySet().stream().sorted((o1, o2) -> {
			MetricEntity e1 = o1.getValue();
			MetricEntity e2 = o2.getValue();
			int t = e2.getBlockQps().compareTo(e1.getBlockQps());
			if (t != 0) {
				return t;
			}
			return e2.getPassQps().compareTo(e1.getPassQps());
		}).map(Entry::getKey).collect(Collectors.toList());
	}

}
